Cui and Zhao BMC Cancer (2019) 19:104 https://doi.org/10.1186/s12885-018-5225-5

RESEARCH ARTICLE Open Access microRNA-342-3p targets FOXQ1 to suppress the aggressive phenotype of nasopharyngeal cells Zheqing Cui and Yulin Zhao*

Abstract Background: microRNA (miR)-342–3p is frequently dysregulated in human cancers. In the present study, we aimed to explore the expression, prognostic significance, and biological relevance of miR-342-3p in nasopharyngeal carcinoma (NPC). Methods: We examined miR-342-3p expression in 79 paired NPC specimens and corresponding normal tissues and analyzed its prognostic impact on overall survival of NPC patients. Gain- and loss-of-function experiments were conducted to determine the biological roles of miR-342-3p. Results: Compared with matched normal nasopharyngeal tissues, miR-342-3p was significantly downregulated in NPC (P = 0.0038). Low miR-342-3p expression was significantly correlated with reduced overall survival (P = 0.0084). Ectopic expression of miR-342-3p significantly suppressed proliferation, colony formation, and invasion of NPC cells. In contrast, depletion of miR-342-3p facilitated NPC cell proliferation and invasion. In vivo xenograft studies confirmed that overexpression of miR-342-3p restrained the growth of NPC xenograft tumors. Mechanistically, FOXQ1 served as a functional target of miR-342-3p. There was a significantly negative correlation between miR-342- 3p and FOXQ1 expression (r = − 0.487, P = 0.004) in NPC specimens. Overexpression of FOXQ1 rescued the inhibitory effects of miR-342-3p on NPC and invasion. Conclusions: miR-342-3p downregulation predicts poor prognosis in NPC patients and shows suppressive activity against NPC growth and invasion through repression of FOXQ1. Restoration of miR-342-3p may represent a potential therapeutic strategy for NPC. Keywords: Invasion, FOXQ1, Growth, miR-342-3p, Nasopharyngeal carcinoma

Background eukaryotic organisms [4]. Deregulation of FOX Nasopharyngeal carcinoma (NPC) is a common tumor has been linked to tumorigenesis, metastasis, and drug of the head and neck in Southeast Asia and China [1]. resistance [5]. For example, FOXO1 phosphorylation Radiotherapy in combination with chemotherapy is the overcomes chemoresistance in cancer cells by block- primary treatment for locally advanced NPC. Due to ing IQGAP1-MAPK interactions [6]. FOXR2 is re- high recurrence and metastasis rates, the prognosis of quired for the growth and spread of prostate cancer advanced NPC is still unsatisfactory, with a 5-year sur- cells [7]. Targeted reduction of FOXM1 was found to vival rate of approximately 50% in Chinese population exert suppressive effects on NPC growth [8]. FOXC2 [2, 3]. However, the exact mechanism for NPC develop- overexpression induces chemoresistance in NPC cells ment and progression has not yet been clarified. [9]. FOXQ1 acts as an oncogene in NPC [10]. These Forkhead box (FOX) proteins are a superfamily of studies suggest FOX proteins as promising targets for transcription factors that are evolutionarily conserved in anticancer treatments. microRNAs (miRs) are a class of short non-coding * Correspondence: [email protected] RNAs that post-transcriptionally regulate expres- Department of Rhinology, First Affiliated Hospital of Zhengzhou University, sion through base pairing to partially complementary Zhengzhou, China

© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Cui and Zhao BMC Cancer (2019) 19:104 Page 2 of 10

sites in the 3′-untranslated region (3′-UTR) of target Cell culture mRNAs [11]. miRs play a critical role in the growth and Four human NPC cell lines (C666, SUNE1, HNE1 and progression of cancers [12]. For instance, it was reported CNE2) and NP69 immortalized nasopharyngeal epithe- that miR-519 inhibits the proliferation of NPC cells by lial cells were obtained from the Shanghai Institutes for repressing URG4/URGCP [13]. miR-342-3p is frequently Biological Sciences, Chinese Academy of Sciences dysregulated in human cancers, such as colon cancer (Shanghai, China). Cells were cultured in RPMI 1640 [14] and pancreatic cancer [15]. This miR shows medium (Thermo Fisher Scientific, Waltham, MA, USA) growth-suppressive activity in hepatocellular carcinoma supplemented with 10% fetal bovine serum (FBS; [16], lung cancer [17], and gallbladder cancer [18]. miR Sigma-Aldrich, St. Louis, MO, USA). The identity of the expression profiling of NPC has revealed the downregu- cell lines have been validated by short-tandem repeat lation of miR-342-3p in NPC [19]. However, the bio- analyses. They are free of mycoplasma contamination. logical function of miR-342-3p in NPC is still unknown. In the present study, we collected 79 paired NPC tis- RNA extraction and real-time PCR analysis sue specimens and adjacent normal tissues and mea- Total RNA was extracted from tissues and cells using sured the expression of miR-342-3p. The prognostic TRIzol reagent (Invitrogen, Grand Island, NY, USA). impact of miR-342-3p was evaluated. To dissect the bio- Reverse transcription was performed using the TaqMan logical roles of miR-342-3p, gain- and loss-of-function Reverse Transcription Kit (Applied Biosystems, Carlsbad, experiments were carried out. CA, USA) and miR-342-3p specific stem-loop primer. Real-time PCR was conducted using the TaqMan Micro- RNA Assay Kit (Applied Biosystems) according to the Methods manufacturer’s instructions. U6 was used an endogenous Tissue specimens control. The expression of miR-342- 3p was normalized We collected 79 paraffin-embedded NPC specimens and against U6. their adjacent normal tissues between 2002 and 2008 from the First Affiliated Hospital of Zhengzhou Univer- Stable expression of miR-342-3p in NPC cells sity (Zhengzhou, China). All cases were confirmed by To generate miR-342-3p stable clones, C666 and CNE2 pathological examination. Follow-up data were retrieved cells were transfected with a miR-342-3p-expressing from medical records. No patient received anticancer plasmid (Cell Biolabs, San Diego, CA, USA) using Lipo- treatment prior to biopsy. There were 51 males and 28 fectamine 2000 Reagent (Invitrogen). Control cells were females, with a median age of 56 years (range, 37–85 transfected with the pEP-miR Null vector (Cell Biolabs). years). Clinicopathologic characteristics of the patients Forty-eight hours post-transfection, cells were selected are shown in Table 1. Written informed consent for in the presence of 2 μg/mL puromycin (Sigma-Aldrich) research was obtained from each patient. This retro- for 10 days. spective study was approved by the Institutional Human Experiment and Ethics Committee of the First Affiliated Transient transfection Hospital of Zhengzhou University. C666 and CNE2 cells were transfected with anti- miR-342-3p inhibitor or negative control inhibitor (50 nM; Exiqon, Vedbaek, Denmark) using Lipofectamine Table 1 Clinicopathological parameters of NPC patients (n = 79) 2000 Reagent. In some experiments, a FOXQ1-expressing Variable No. of cases plasmid or empty vector was transfected to C666 cells Age (years) with stable expression of miR-342-3p. The FOXQ1-ex- >50 47 pressing plasmid was generated by inserting a full-length ≤ 50 32 open reading frame of FOXQ1 (lacking the 3′-UTR) into Gender pcDNA3.1(+) expression vector. Twenty-four hours after transfection, cells were tested for gene expression, prolif- Male 51 eration, and invasion. Female 28 Clinical stage Cell proliferation and colony formation assays I/II 24 Cells were seeded onto 96-well plates (4 × 103 cells/well) III/IV 55 and cultured for 3 and 5 days. Each well was added with Lymph node status 3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide (MTT) solution (0.5 mg/ml, Sigma-Aldrich) Absent 19 and incubated for 4 h at 37 °C. Dimethyl sulfoxide was Present 60 used to dissolve the resultant crystals. Absorbance was Cui and Zhao BMC Cancer (2019) 19:104 Page 3 of 10

recorded at 570 nm. For evaluation of colony formation capacity, cells were plated onto 6-well plates (500 cells/ well) and cultured for 10 days. After staining with 1% crystal violet (Sigma-Aldrich), the number of colonies was determined using a microscope.

Transwell invasion assay We used the methodology previously described by Zhao and colleagues [20]. Cells in serum-free medium con- taining 10 μg/ml mitomycin C (Sigma-Aldrich) were seeded in the upper chamber of 24-well Transwell plates (2 × 104 cells/well). The inserts (8 μm in pore size) were precoated with Matrigel (BD Biosciences, San Jose, CA, USA). The lower chamber was filled with RPMI 1640 medium containing 10% FBS. The cells were allowed to invade through the Matrigel-coated inserts for 24 h. Afterwards, invaded cells were stained with 1% crystal violet and counted under a microscope.

Dual-luciferase reporter assay Luciferase reporter assay was performed as previously described [20]. The 3’-UTR of FOXQ1 mRNA was inserted into the pMIR-REPORT Luciferase miRNA Expression Reporter Vector (ThermoFisher Scientific, Waltham, MA, USA). A mutant form with disruption of the miR-342-3p binding site was constructed using the QuikChange site-directed mutagenesis kit (Stratagen, Santa Clara, CA, USA). C666 cells were co-transfected with the reporter constructs together with the miR-342- 3p-expressing plasmid or empty vector. Luciferase activ- ities were measured using the Dual-Luciferase Reporter Assay System (Promega, Fitchburg, WI, USA) 48 h after transfection. The relative luciferase activity was determined after normalization against Renilla lucifer- ase activity.

Tumorigenic studies in nude mice For tumorigenic studies, C666 and CNE2 cells with stable overexpression of miR-342-3p or empty vector (2 × 106 cells/mouse) were subcutaneously inoculated into the flanks of male BALB/c nude mice (5 weeks of age; Shanghai Laboratory Animals Center of Chinese Academy of Sciences, Shanghai, China). Tumor growth was monitored for 5 weeks. After the last measurement of tumor volume, animals were are euthanized by car- bon dioxide inhalation followed by cervical dislocation. The xenograft tumors were resected and weighed. After- Fig. 1 miR-342-3p is downregulated in NPC and predicts poor prognosis. wards, tumor samples were fixed, embedded in paraffin, a Measurement of miR-342-3p levels in 79 paired NPC specimens and adjacent normal nasopharyngeal tissues by real-time PCR analysis. b and subjected to immunostaining for Ki-67 using an Kaplan-Meier curves for overall survival in the NPC patients with high anti-Ki-67 monoclonal antibody (Thermo Fisher Scien- (n = 38) vs. low (n = 41) miR-342-3p expression. The differences between tific; 1:400 dilution). The experiment protocol was the survival curves were determined by the log-rank test. c Measurement approved by the Animal Care and Use Committee of of miR-342-3p in indicated cell lines. *P < 0.05 vs. NP69 cells Zhengzhou University. Cui and Zhao BMC Cancer (2019) 19:104 Page 4 of 10

Western blot analysis quantified by densitometric analysis using the Quantity samples from NPC tissues and cells were prepared One software (Bio-Rad Laboratories, Hercules, CA, USA). in radioimmunoprecipitation assay buffer (Sigma-Aldrich) supplemented with the Protease and Phosphatase Inhibi- tor Cocktail (Abcam, Cambridge, UK). Protein samples Statistical analysis were separated by SDS-polyacrylamide gel electrophoresis Data are expressed as the mean ± standard deviation and transferred onto polyvinylidene difluoride mem- (SD). Differences in the means were determined using branes. Membranes were probed with rabbit anti-FOXM1 the Student’s t test or one-way analysis of variance polyclonal antibody (Abcam; 1:500 dilution), anti-FOXQ1 (ANOVA) followed by Tukey’s multiple comparison test. polyclonal antibody (Abcam; 1:500 dilution), or anti- The correlation between miR-342-3p and FOXQ1 pro- β-actin polyclonal antibody (Thermo Fisher Scientific; tein levels in NPC specimens was determined by Pear- 1:5000 dilution), followed by incubation with horseradish son’s correlation coefficient analysis. Survival curves peroxidase-conjugated goat anti-rabbit IgG (Sigma-Al- were plotted using the Kaplan-Meier method and com- drich). Signals were visualized by enhanced chemilumines- pared using the log-rank test. P < 0.05 was considered cence (Thermo Fisher Scientific). Protein bands were statistically significant.

Fig. 2 miR-342-3p suppresses NPC cell growth and invasion in vitro. a Real-time PCR analysis of miR-342-3p levels in NPC cells transfected with the miR-342-3p-expressing plasmid or vector. b Analysis of proliferation by MTT assay in NPC cells transfected with the miR-342-3p-expressing plasmid or vector. c Colony formation assay performed in NPC cells transfected with the miR-342-3p-expressing plasmid or vector. Left, representative images of colonies. d Transwell invasion assay. Ectopic expression of miR-342-3p significantly decreased the invasion of C666 and CN2 cells, compared to control cells. Column: mean of three independent experiments performed in three replicates. Error bar: SD. *P < 0.05 Cui and Zhao BMC Cancer (2019) 19:104 Page 5 of 10

Results miR-342-3p than NP69 non-malignant cells (Fig. 1c). miR-342-3p is downregulated in NPC and predicts poor The upregulation of miR-342-3p in both C666 and prognosis CNE2 cells stably transfected with the miR-342-3p-ex- A total of 79 paired non-malignant and NPC specimens pressing plasmid (Fig. 2a). As determined by MTT assay, were analyzed for miR-342-3p expression. Compared with the number of viable cells was significantly reduced in corresponding normal nasopharyngeal tissues, NPC tis- miR-342-3p-overexpressing cells relative to control cells sues displayed a significant downregulation of miR-342-3p after culturing for 3 and 5 days (P < 0.05; Fig. 2b). Colony (P = 0.0038; Fig. 1a). According to the median level of formation assay further showed that miR-342-3p overex- miR-324-3p in NPC specimens, the 79 patients were di- pression reduced the ability of C666 and CNE2 cells to vided into two groups. The prognostic significance of form colonies (P < 0.05; Fig. 2c). To determine whether miR-342-3p expression was then evaluated using the miR-342-3p affects the invasion of NPC cells, Trans- Kaplan-Meier method and log-rank tests. It was found well invasion assay was conducted. The results dem- that low miR-342-3p levels were significantly correlated onstrated that ectopic expression of miR-342-3p with shorter overall survival (P = 0.0084; Fig. 1b) of the significantly inhibited the invasion of C666 and NPC patients. These results suggest an important role for CNE2 cells by 74 and 68%, respectively (P < 0.05; miR-342-3p in the pathogenesis of NPC. Fig. 2d). To further confirm the suppressive roles of miR-342-3p, miR-342-3p suppresses NPC cell growth and invasion in cell proliferation and invasion were examined after inhib- vitro ition of miR-342-3p. It was found that transfection with Next, we investigated the effect of restoration of anti-miR-342-3p significantly decreased the expression of miR-342-3p on the aggressive phenotype of NPC cells. miR-342-3p (Fig. 3a), which was accompanied by in- Real-time PCR analysis that NPC cell lines including creased cell proliferation (Fig. 3b) and invasion (Fig. 3c) in C666 and CNE2 showed significantly lower levels of both C666 and CNE2 cells.

Fig. 3 Depletion of miR-342-3p promotes NPC cell growth and invasion. a Real-time PCR analysis of miR-342-3p levels in C666 and CN2 cells transfected with control (Anti-control) or anti-miR-342-3p inhibitors. b Analysis of proliferation by MTT assay in C666 and CN2 cells transfected with control or anti-miR-342-3p inhibitors. c Transwell invasion assay was employed to assess the invasive ability of C666 and CN2 cells transfected with control or anti-miR-342-3p inhibitors. Column: mean of three independent experiments performed in three replicates. Error bar: SD. *P < 0.05 Cui and Zhao BMC Cancer (2019) 19:104 Page 6 of 10

Fig. 4 miR-342-3p restrains the growth of NPC xenograft tumors in vivo. a Measurement of the growth of xenograft tumors formed by C666 and CNE2 cells stably transfected with the miR-342-3p-expressing plasmid or vector (n = 4; error bar: SD). b Final tumor weight was determined at 5 weeks after cell injection. Column represents the mean value for 4 mice (error bar, SD). Top, macroscopic view of the tumors. c Immunohistochemical staining for Ki-67 in the C666 and CNE2 xenograft tumors. Column represents the mean value for 4 mice (error bar, SD). Scale bar = 100 μm. *P <0.05 Cui and Zhao BMC Cancer (2019) 19:104 Page 7 of 10

Fig. 5 miR-342-3p targets FOXQ1 in NPC cells. a and b Western blot analysis of indicated proteins in C666 and CNE2 cells transfected with indicated constructs. Numbers represent fold change in protein levels. Data represent mean of three independent experiments. c Luciferase reporter assay performed in C666 cells demonstrated that the reporter construct harboring wild-type (wt) FOXQ1 3’-UTR but not the mutant (mt) was suppressed by overexpression of miR-342- 3p. *P < 0.05. N.S. indicates no significance. d Determination of the relationship between miR-342-3p and FOXQ1 protein expression in NPC specimens (n = 79) by Pearson’s correlation coefficient analysis. e Western blot analysis of FOXQ1 protein levels in indicated cells

miR-342-3p restrains the growth of NPC xenograft tumors in vivo Next, we assessed the effects of miR-342-3p overexpres- sion on tumor growth in vivo. All the 4 mice injected with empty vector-transfected C666 cells developed a palpable tumor 1 week later, whereas the onset of tumor development was delayed by 1 week in the correspond- ing miR-342-3p overexpression group (Fig. 4a). Over an observation period of 5 weeks, the tumor growth rate was slower in the miR-342-3p overexpression group than than in the vector group (P < 0.05; Fig. 4a). When empty vector- or miR-342-3p-transfected CNE2 cells were implanted into nude mice, a minor tumor was palpable at 1 week in both the groups (Fig. 4a). However, there was a marked reduction in the tumor growth rate in the miR-342-3p overexpression group, compared to the corresponding vector group. Final tumor weight was reduced in the miR-342-3p overexpression group (0.39 ± 0.07 and 0.32 ± 0.06 g in C666 and CNE2 tumors, re- spectively) than in the control group (0.88 ± 0.04 and 1.12 ± 0.08 g in C666 and CNE2 tumors, respectively; Fig. 4b). Immunohistochemical staining confirmed that overexpression of miR-342-3p led to a significant decline in the percentage of Ki-67-positive cells in the xenograft tumors (Fig. 4c). These data indicated that miR-342-3p shows growth-suppressive activity in NPC cells in vivo.

miR-342-3p targets FOXQ1 in NPC cells It has been documented that both FOXM1 and FOXQ1 serve as two targets of miR-342-3p in colorectal cancer [21]. Given the importance of FOX proteins in NPC development, we tested whether miR-342-3p exerts its suppressive activity through targeting of FOXM1 and FOXQ1. Western blot analysis showed that overexpres- sion of miR-342-3p markedly downregulated the expres- sion of FOXQ1, but had little effect on FOXM1 expression in C666 cells (Fig. 5a). In contrast, delivery of anti-miR-342-3p promoted the expression of FOXQ1 (Fig. 5b) in C666 cells. Similar findings were observed in CNE2 cells (Fig. 5a and b). Luciferase reporter assay showed that overexpression of miR-342-3 p significantly suppressed the wild-type FOXQ1 3’-UTR reporter con- struct, but not the mutant form (Fig. 5c). We measured Cui and Zhao BMC Cancer (2019) 19:104 Page 8 of 10

Fig. 6 FOXQ1 rescues NPC cells from miR-342-3p-induced growth and invasion suppression. a Western blot analysis of FOXQ1 protein levels in C666 cells co-transfected with miR-342-3p- and FOXQ1- expressing plasmid or vector. Numbers represent fold change in protein levels. b Analysis of proliferation by MTT assay in C666 cells transfected with indicated constructs. c Transwell invasion assay was employed to assess the invasive ability of C666 cells transfected with indicated constructs. Top, representative images of invaded cells. Column: mean of three independent experiments performed in three replicates. Error bar: SD. *P < 0.05

the protein levels of FOXQ1 in NPC specimens by Western blotting. Analysis of the relationship between miR-342-3p and FOXQ1 expression in NPC specimens revealed that there was a significantly negative cor- relation between miR-342-3p and FOXQ1 expression (r = − 0.487, P = 0.004; Fig. 5d). However, no significant correlation was detected between the expression of miR-342-3p and FOXM1 in NPC tissues (P >0.05). In addition, we found an upregulation of FOXQ1 in both C666 and CNE2 cells compared to NP69 cells (Fig. 5e). These data suggest that FOXQ1 is a direct target of miR-342-3p in NPC.

FOXQ1 rescues NPC cells from miR-342-3p-induced growth and invasion suppression Having identified the downregulation of FOXQ1 by miR-342-3p, we next addressed whether enforced expression of FOXQ1 can rescue the suppressive effect of miR-342-3p on NPC cells. To this end, we overex- pressed a miR-resistant variant of FOXQ1 in C666 cells together with ectopic expression of miR-342-3p (Fig. 6a). Overexpression of FOXQ1 significantly restored the pro- liferation (Fig. 6b) and invasion (Fig. 6c) capacity of miR-342-3p-overexpressing C666 cells. These observations suggest that FOXQ1 mediates the activity of miR-342-3p in the regulation of NPC growth and invasion.

Discussion In this study, we showed that miR-342-3p was signifi- cantly underexpressed in NPC tissues compared to adjacent normal nasopharyngeal tissues. In line with our findings, the dysregulation of miR-342-3p is also described in colon cancer [14], pancreatic cancer [15], and hepatocellular carcinoma [22]. We further ana- lyzed the relationship between miR-342-3p expression and survival of NPC patients. It was found that downregulation of miR-342-3p had a poor prognostic impact on the survival of patients with NPC. Simi- larly, low miR-342-3p expression is significant associ- ated with reduced overall survival in patients with hepatocellular carcinoma [22]. These observations favor the idea that miR-342-3p may govern the pro- gression of NPC. Cui and Zhao BMC Cancer (2019) 19:104 Page 9 of 10

To clarify the biological relevance of miR-342-3p activity of miR-342-3p in NPC. Genome-wide identifica- downregulation in NPC, we performed gain- and loss- tion of target would be necessary to uncover the of-function experiments. The results demonstrated that mechanism by which miR-342-3p governs the aggressive ectopic expression of miR-342-3p significantly sup- phenotype of NPC cells. The mechanism underlying the pressed proliferation, colony formation, and invasion of downregulation of miR-342-3p in NPC is still elusive. A NPC cells. In contrast, depletion of miR-342-3p led to a previous study has indicated that long non-coding RNAs significant enhancement of NPC cell proliferation and such as FTX [31] show the capacity to repress the invasion. In vivo tumorigenic studies confirmed that expression of miR-342-3p. The reduced expression of miR-342-3p overexpression hampered the growth of miR-342-3p can also be explained as a result of abber- NPC xenograft tumors. These data indicate that miR- rant methylation of the promoter region of its host gene, 342-3p acts as a tumor suppressor in NPC. In support of EVL [32]. Ongoing studies are conducted to address this our point, several previous studies have documented that issue. Another limitation of this study was the enroll- miR-342-3p plays a tumor-suppressive role in multiple ment of patients from a single center. malignancies including hepatocellular carcinoma [16], colorectal cancer [21], osteosarcoma [23], and small cell Conclusions lung cancer [24]. However, a recent study has provided In summary, our data demonstrate that miR-342-3p has a evidence that miR-342-3p has no significant impact on poor prognostic impact on the survival of NPC patients. the progression of pancreatic acinar carcinoma in a Restoration of miR-342-3p suppresses NPC cell growth mouse model [25]. Therefore, the functional conse- and invasion via targeting of FOXQ1 and may have thera- quence of miR-342-3p depends on cellular contexts. peutic benefits in the treatment of this malignancy. It is well accepted that a single miR has the ability to modulate a large number of target genes [11]. Different Abbreviations 3′-UTR: 3′-untranslated region.; FOX: forkhead box; miRs: microRNAs; targets have been identified to mediate distinct biological NPC: nasopharyngeal carcinoma activities of miR-342-3p [23, 26, 27]. For instance, miR-342-3p regulates lumen formation in mammary Acknowledgements gland morphogenesis through repression of ID4 and None. DNMT1 [26]. This miR shows the ability to induce Funding adipogenesis of mesenchymal stem cells by suppressing No funding was obtained for this study. CtBP2 [27]. Both FOXM1 and FOXQ1 mediate the tumor-suppressive activity of miR-342-3p in colorectal Availability of data and materials cancer cells [21]. Similarly, we found that miR-342-3p The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. overexpression caused a significant downregulation of FOXQ1 in both C666 and CNE2 cells. However, the Authors’ contributions level of FOXM1 remained unchanged in response to ZC and YZ made substantial contributions to conception design, acquisition of data, analysis and interpretation of data, and write/edit manuscript. All miR-342-3p overexpression. The selective repression of authors have read and approved the final manuscript. FOXQ1 implies its critical role in mediating the activity of miR-342-3p in NPC. Clinical evidence indicates a Ethics approval and consent to participate negative correlation between miR-342-3p and FOXQ1 Written informed consent for research was obtained from each patient. This retrospective study was approved by the Institutional Human Experiment expression in NPC specimens. Rescue experiments using and Ethics Committee of the First Affiliated Hospital of Zhengzhou a miR-resistant variant of FOXQ1 demonstrated that University. enforced expression of FOXQ1 significantly reversed the suppressive effect of miR-342-3p on NPC cell prolifera- Consent for publication Not applicable. tion and invasion. FOXQ1 functions as an oncogene in colorectal carcinoma [28], gastric cancer [29], and NPC Competing interests [10]. It has been documented that FOXQ1 can facilitate The authors declare that they have no competing interest. the metastasis of gastric cancer cells through upregula- tion of Snail [29]. FOXQ1 is upregulated in NPC and Publisher’sNote can be regulated by a number of miRs including Springer Nature remains neutral with regard to jurisdictional claims in miR-124 [10] and miR-506 [30]. 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